In the mid-2370s, Valerie Archer was impersonated by a member of Species 8472 in the training simulation on the Terrasphere 8, designed to accurately simulate Earth. The polymorphed members of Species 8472 were conducting a role-playing mission to better understand their enemy, the Federation and Starfleet. Valerie Archer was one of the officers impersonated by Species 8472.
The impersonated Archer took up many interests in humanoid culture, including such reading material as Beyond the Galactic Edge, Humanity's Quest for Infinity and A Cave Beyond Logic: Vulcan Perspectives on Platonic Thought. She was also partial to Klingon martinis. (VOY episode: "In the Flesh")
In 2375, Commander Chakotay, posing as Commander Jason Hayek, encountered Archer on Terrasphere 8. Chakotay attempted to discover what Species 8472 was planning by developing a rapport with Archer. During their first meeting, an officer began to morph back to his original form. Archer asked Chakotay whether he had ever reverted. She also told him that she disliked breathing oxygen and sleeping as if she were Human. Later, on a date with Chakotay, she gave herself a shot in the thigh in order to maintain her form. Chakotay discussed with her whether it was necessary to invade Earth, and Archer stated that Humans had allied themselves with the Borg and must be destroyed. Archer wanted to give Chakotay a goodnight kiss, wondering what it would be like. When she kissed him, she rubbed her hands on his face. A scan of her hand revealed that Chakotay was Human.
After Captain Kathryn Janeway and Species 8472 reached an agreement and settled their differences, Chakotay and Archer kissed once again. He was impressed with her mastery of the art of kissing. (VOY episode: "In the Flesh")
In 2381 Valerie Archer was encountered by the Project Full Circle fleet after both Voyager and USS Galen were hijacked by Willem Batiste whom was in fact a Species 8472 agent that had been left in the Alpha Quadrant prior to the peace accord. She explained the nature of several of the agents and was initially reluctant to allow for Bastiste to return to fluidic space, claiming that he had spent too much time among humans and would corrupt their realm as much as any human presence would. Chakotay was able to convince her to take him back to their realm and help reacclimate him to their space, citing Voyager's own return to Earth and the difficulties they faced as precident. Valerie commented that both humanity and Species 8472 had more in common then they would care to admit and warned Chakotay that humans should not attempt to contact Fluidic space, when Species 8472 is ready to talk, they will approach humanity themselves. (VOY novel: Unworthy)